September 28, 2005
Greenland Melt Extent, 2005
Konrad Steffen and Russell Huff
Cooperative Institute for Research in Environmental Sciences (CIRES),
University of Colorado at Boulder, CO 80309-0216
Passive microwave satellite data are used to map snowmelt extent and duration on the Greenland ice sheet. The total melt extent of the ice sheet, experiencing at least 1 melt day between April 1 - September 25 shows a record extent in 2005 for the 27-year long time PM data set. The 2005 melt extent exceeds the previous record of 2002. (Steffen et al., 2004; Hanna et al., 2005)
The total melt area for the same time period in 2005 is slightly lower than 2002 (0.6%) and 1991 (1.1%) as of September 25th. However, we expect a record total melt area for 2005 given the fact that the southern and western part of Greenland are still melting in late September, whereas 2002 and 1991 experienced almost no melt in late September and during October. The melt during October 2003 was 2.3 times that of 1991 and 4.3 times that of 2002. We expect the melt of 2005 to be equal or even larger.
There was extensive melt for 7 days during 2005 that covered ALL of southern Greenland including South Dome at an elevation of 2900 m for 3 days. This event resulted in the largest melt area recorded on the ice sheet surpassing the previous record in 2002. The 3-D view of Greenland melt extent shows the total melt area for 2005 and highlights the regions that never melted in the previous 26-year long PM record.
The melt extent for 1992 (minimum extent) and for 2005 (maximum extent) are displayed in the same 3-D view of Greenland in light red (1992) and dark red (2005) color.
A record for total melt was observed for the north-west of the Greenland ice sheet in the Thule region for 2005. There were 24 PM satellite pixels primarily in the higher
elevations in the northwest that melted in 2005 for the first time in the satellite record (27 years).
A summary of the melt extent and total melt for the entire Greenland ice Sheet and for the north-western part (Thule) and the western part (Jakobshavn region) is provided in the following PDF file.
Detection of surface melt at large spatial scales is most effectively accomplished through the use of satellite microwave data, which has a clear melt signature that arises from the transition from volume- to surface-scattering during melt onset. As such, wet-snow emission approaches black body behavior, and this change in emission characteristics is detectable by most microwave sensors. These changes in emission characteristics have formed the basis of several passive-microwave-based melt assessment algorithms.
CIRES is a joint institute of CU [ About CU ] and the National Oceanic and Atmospheric Administration [ About NOAA ] .
Steffen, K., S.V. Nghiem, R. Huff, and G. Neumann, The melt anomaly of 2002 on the Greenland Ice Sheet from active and passive microwave satellite observations, Geophys. Res. Lett., 31(20), L2040210.1029/2004GL020444, 2004.
Hanna,H., P.Huybrechts, I. Janssens, J..Cappelen, K. Steffen, and A. Stephens, Runoff and mass balance of the Greenland ice sheet: 1958–2003, J. Geophys. Res., 110, D13108, doi:10.1029/2004JD005641, 2005.
